I'd like to participate in the following projects, that would all be running at the same time:
- Rosetta@home
- WCG Mapping Cancer Markers
- WCG Help Fight Childhood Cancer
- WCG FightAIDS@home

As you can see, i have a quad core CPU and i'd like to setup each project to run on 1 thread, so all 4 projects would be running equally without the 60 minute switching between the projects. I have a limit set to 10% CPU usage. I know i won't crunch as much, but i want the lowest footprint but still crunch. I complete around 4 projects a day this way so i think it's still quite productive without affecting my computer or the power bill much at all.

Anyway, how should i set my config to run the projects like i want them? BOINC or/and the project settings. Can't seem to find anything on this topic through Google.

You can run the last three just by opting into all projects for WCG. For the first one on your list, you will probably not be able to run it, unless you figured out a way to run two instances of the client and have two different accounts.

No, it will run four threads if you let it run max cpu's, since you have a 4-core proc. Actually, if we're talking about the i7 920 in your system specs, that should be a 4C/8T CPU, so you would get 8 work units at the same time. You opt in for all projects, and you run whatever the server can give you at the moment.

Again, I'm not sure if there's a way to run two instances to get two accounts to run different sets of projects (WCG is one project, Rosetta is another).